US detects 'highly unusual' North Korean submarine activity
By Zachary Cohen and Ryan Browne, CNN
Updated 10:16 PM ET, Tue August 1, 2017
Washington (CNN)The US military has detected "highly unusual and unprecedented levels" of North Korean submarine activity and evidence of an "ejection test" in the days following Pyongyang's second intercontinental ballistic missile launch this month, a defense official told CNN on Monday.
An ejection test examines a missile's "cold-launch system," which uses high pressure steam to propel a missile out of the launch canister into the air before its engines ignite. That helps prevent flames and heat from the engine from damaging either the submarine, submersible barge or any nearby equipment used to launch the missile.
http://www.cnn.com/2017/07/31/politics/north-korea-ejection-test-submarine-activity/index.html
